The overall objective of the present research project is to evaluate the extent of binocular vision in subjects with: Stereoblindness, alternation, amblyopia, and strabismus. The extent of binocularity will be evaluated both clinically and psychophysically. The psychophysical evaluation will be made by measuring the amount of interocular transfer of the motion aftereffect as a function of the stimulus size, spatial periodicity, and contour orientation. The stimuli are sufficiently specific so as to excite only a narrow population of neurons. The psychophysical results will be correlated with the clinical findings in order to determine which populations of neurons are not functionally binocular for each kind of binocular disorder.